Energy Resolved Neutron Imaging for Strain Reconstruction Using the Finite Element Method

Abstract

A pulsed neutron imaging technique is used to reconstruct the residual strain within a polycrystalline material from Bragg edge strain images. This technique offers the possibility of a nondestructive analysis of strain fields with a high spatial resolution. A finite element approach is used to reconstruct the strain using a least square method constrained by the conditions of equilibrium. The procedure is developed and verified by validating for a cantilevered beam problem. It is subsequently demonstrated by reconstructing the strain from experimental data for a ring-and-plug sample, measured at the spallation neutron source RADEN at J-PARC in Japan. The reconstruction is validated by comparison with conventional constant wavelength strain measurements on the KOWARI diffractometer at ANSTO in Australia. It is also shown that the addition of a simple Tikhonov regularization can improve the reconstruction. *

Neutron Bragg-edge transmission imaging for microstructure and residual strain in induction hardened gears

“…From the viewpoint of transmission ability, the measurement for steel samples with the thickness approximately up to 20 mm is possible. In addition, three-dimensional residual strain experiment for the development of strain tomography techniques has started at RADEN that could be applied to complex engineering components in the future 36 , 37 .…”

An Investigation of Radial Basis Function Method for Strain Reconstruction by Energy-Resolved Neutron Imaging

“…The complicated meshing rules are not required while performing RBF, and here lies the advantage of the proposed method over the framework of finite elements. The use of meshless methods over the finite-element approach for reconstruction tensor strain field [39][40][41] has many other benefits. We can quickly increase the support domain, change basis functions, adopt nodal densities, and many more.…”

Geometrically Flexible and Efficient Numerical Solution Technique for Bragg Edge Neutron Transmission Strain Tomography

“…The descriptions of the algorithms, the comparison of approaches and the improvements in the resolution of the images are intended to serve as an entry-point guide for researchers wishing to continue this work further. Some of this research has been published in [1][2][3][4].…”